A window air conditioning unit can be just the thing to make your home comfortable during the heat of summer. These units are generally designed to cool only one room, although there are larger models that can cool larger areas. The main problem occurs if ice begins building up on the outside of the unit. This will bring the fan to a halt and soon you will be overheating again. The following guide can help you determine the cause so you can be cool again.

Problem #1: It's too cool outside

The most obvious issue is that the outside air temperature has dropped below the interior temperature. This can sometimes happen at night or if a cold front comes in unexpectedly. Your AC may respond by icing up on the outside. The fix is relatively simple – turn off the air conditioner and don't run it again until it has thawed out and the outside air temperature requires inside cooling.

Problem #2: The refrigerant is low

Air conditioners have a refrigerant, usually Freon, that runs through the condenser coils. If there is a leak and Freon is lost, then the pressure is off inside the unit. This can lead to the evaporator coil becoming too cold so that any moisture in the air running around the inside or exterior of the unit instantly freezes onto the coil. You will need to have an HVAC tech test for Freon leaks, repair them, and then recharge the unit with fresh refrigerant.

Problem #3: There's poor circulation

Window units need proper air flow over the evaporator coil. Without it, the coil becomes too cold and causes the unit to freeze up. Make sure there is nothing blocking the exterior of the unit, since this is the main source of air flow. Inside, check the filters and clean them regularly so there is good airflow. Most window units have washable and reusable filters, but you have to let them dry before placing them back in the AC and turning it back on.

Problem #4: The fan is broken

The fan is necessary for spreading around the cold air. If it isn't working properly (or at all) then the air collects in the unit and causes it to freeze up. You can inspect the fan yourself by turning off an unplugging the unit. Remove the housing and verify that the fan spins freely. Sometimes, something gets wrapped around it and causes it to jam – simply removing it fixes the fan. If you can't easily see a problem, then bring in a tech to fix or replace the fan.

Make sure that you shut off the unit immediately when it begins to freeze, and don't try to run it again until it has thawed completely. Trying to run a frozen window AC can result the motor burning out. Contact an HVAC contractor in your area if you need more help. Click here for more information.